2SK3940 MOSFET — Specifications & Equivalents

About the 2SK3940

The 2SK3940 is an N-channel MOSFET with a drain–source voltage (V_DS) rating of 75 V, a continuous drain current (I_D) of 70 A and an on-resistance (R_DS(on)) of 0.007 Ω. It can dissipate up to 150 W and is rated to a junction temperature of 175 °C. It is available in SC65 and TO3P packages, so confirm the pinout of the exact variant you order.

At a glance

• Type: N-channel MOSFET
• Max drain–source voltage (V_DS): 75 V
• Max continuous drain current (I_D): 70 A
• On-resistance (R_DS(on)): 0.007 Ω
• Power dissipation (P_D): 150 W
• Max junction temperature (T_J): 175 °C
• Package: SC65, TO3P
• Manufacturer: Multi-source (JIS registered part number)

Typical applications

With its 75 V drain–source rating the 2SK3940 sits in the mid-range class of switching MOSFETs, typically found in 24 V and 48 V industrial and battery systems, motor drives and H-bridges and load and hot-swap switching.

The 70 A current rating puts it in high-current territory, where conduction loss (I² × R_DS(on)) and thermal design usually matter more than switching loss. Budget for adequate copper area and a heatsink.

The low 0.007 Ω on-resistance keeps conduction loss down, which suits synchronous rectification and continuous high-current paths.

Gate drive and switching notes

Keep gate–source voltage within the ±20 V maximum; exceeding it punctures the gate oxide and destroys the device permanently.

Switching behaviour is characterised by a rise time of 20 ns and an output capacitance (C_oss) of 970 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.

Choosing a replacement for the 2SK3940

A drop-in substitute for the 2SK3940 must be the same N-channel type and offer a drain–source rating of at least 75 V, a continuous drain current rating of at least 70 A and an on-resistance no higher than 0.007 Ω if efficiency and heat matter.

Mechanically, check the replacement against the SC65 and TO3P footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Because 2SK3940 is a JIS-registered part number rather than one vendor's proprietary series, it is produced by several manufacturers. Datasheet figures vary slightly between them, so check the datasheet of the brand you actually buy — this also makes like-for-like sourcing easier.

Where the application switches inductive loads or runs near the voltage limit, keep extra headroom rather than choosing a part that only just meets the original numbers.

Frequently asked questions

What is the 2SK3940?

The 2SK3940 is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 75 V drain-source and 70 A continuous drain current.

What is the maximum voltage of the 2SK3940?

The 2SK3940 has a maximum drain-source voltage (Vds) of 75 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.

How much current can the 2SK3940 handle?

It is rated for 70 A of continuous drain current, with power dissipation limited to 150 W. Real-world capability depends on your heatsinking and ambient temperature.

What is the on-resistance of the 2SK3940?

On-resistance (Rds(on)) is 0.007 Ω. Multiply by the square of your load current to estimate conduction loss.

What package does the 2SK3940 come in?

It is listed in SC65 and TO3P. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the 2SK3940?

No verified equivalents are listed yet. Choose a part of the same polarity that meets or exceeds every rating above and shares a compatible package and pinout.